William Boye and his orange-vested troop of 40 will spend the next seven months visiting every house, condominium, apartment building, business and vacant lot in Broward County.

All 542,184 of them.

Their job: Figure out how much each piece of property is worth -- and, ultimately, how much the owner will pay in property taxes to cover the cost of everything from schools to police protection.

Monday signaled the official start, with specially hired appraisers fanning out in north Broward to peer over fences and behind houses in search of improvements that would make the properties more valuable.

When they are done, some property owners will feel the sting that comes with Broward`s once-a-decade reappraisal of all taxable property in the county.

The best guess: People who live on canals and the ocean could be socked with sizable increases in their property tax bills.

The value of waterfront property has jumped as much as 24 percent during the last year, so the assessed value of such homes is expected to soar throughout eastern Broward.

Assessments and tax bills also could increase in cities such as Coral Springs, Parkland and Davie, where some sections have not been reappraised for three years.

``If an assessment goes up and the (tax) rate stays the same, taxes will go up,`` said Boye, an administrative assistant to Property Appraiser William Markham.

The 542,184 taxable properties the appraisers will visit now are assessed at nearly $50 billion. That is a dramatic increase over 1979, when 413,179 properties had a value of just more than $16 billion.

It is anyone`s guess how much that figure will climb after the reappraisal, which includes 243,181 single-family homes, 198,403 condominiums and 44,694 commercial buildings.

Residents will find out in August, when notices listing proposed tax increases are sent to every property owner for fiscal 1990-91.

Others who could face increases include homeowners who live in areas where only a few houses have been sold. Surrounding properties often get reassessed upward after several neighboring houses are sold.

``I will put it this way: In areas where there has not been a lot of (sales) in the last few years, there will be some increase,`` Boye said.

In Davie, for example, a home on Southwest 12th Way that sold for $100,000 in September has an assessed value of $63,070. That assessment is too low and will likely go up, Boye said.

But the hardest hit likely will be waterfront property owners with ocean access, said Ray Barkett, a real estate broker for 20 years with Keyes Co.

``Over the past year or two, there has been substantial inflation of waterfront homes, in some cases as high as 2 percent a month,`` Barkett said.

``The best commercial investment in South Florida in recent years has been the renovation of some of the older waterfront homes. Investors are buying older homes and then putting them up for resale.``

He said even condominiums are increasing in value when they are on the water, even though many condominiums elsewhere are not.

Homes that have not been reassessed recently could have their assessments jump because prices have been increasing 6 percent to 8 percent a year in communities such as Plantation, Coral Springs and Davie.

The county tries to assess properties once every three years to keep them at 100 percent of their market value, as required by the state.

But so many properties have been sold recently that officials have not been able to keep up.

``What we`re striving for is uniformity,`` said Joseph Zdanowicz, chief appraiser in Markham`s office. ``By the time we`re through, we`ll have been over every single piece of property in Broward County.``

He said it will not be a repeat of 1980, when property owners strongly protested as assessments skyrocketed.

``Yes, there is going to be an increase in assessments, but no, you are not going to have property increases of 200 to 300 percent like it was in 1980,`` Zdanowicz said.

For the first time, driveways -- their size and material -- can also increase property values.

Appraisers make an educated judgment based on their expertise. They check for new windows and roofs, additions, a pool -- anything that could increase, or decrease, the selling price.

Zdanowicz said the last time the reappraisal was done, in 1980, assessments skyrocketed, causing some property owners to overpay and embroiling the county in a court battle that just ended.

More than 238,000 property owners are getting refunds this year that total nearly $32 million for property taxes they overpaid in 1980.

VERIFYING APPRAISERS

Because of concerns about criminals posing as appraisers, the Broward County Property Appraiser`s Office says everyone should know that:

--Each appraiser will wear an orange vest, stamped with the name and telephone of the office. They also are asked, but not required, to wear a special white cap.

--Each vest will be tagged with a Broward County employee identification card.

--Appraisers will carry pamphlets explaining the procedure.

--Appraisers are not allowed to enter any home, even if they are invited inside.

--Appraisers also will carry cards with information about the property, which they will use as the basis for updating property logs.